AII retinal amacrine cell-specific promoter

ABSTRACT

The present invention provides an isolated nucleic acid molecule comprising, or consisting of, the nucleic acid sequence of SEQ ID NO: 1 or a nucleic acid sequence of at least 200 bp having at least 70% identity to the sequence of SEQ ID NO: 1, wherein the isolated nucleic acid molecule specifically leads to the expression in retinal amacrine bipolar cells of a gene when operatively linked to a nucleic acid sequence coding for the gene.

This application is a U.S. National Phase filing of InternationalApplication No. PCT/IB2015/050963 filed 9 Feb. 2015, which claimspriority to EP Application No. 14154556.6 filed 10 Feb. 2014, thecontents of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to a nucleic acid sequence leading to theexpression of genes specifically in amacrine cells of the retina.

BACKGROUND OF THE INVENTION

For expression purposes recombinant genes are usually transfected intothe target cells, cell populations or tissues, as cDNA constructs in thecontext of an active expression cassette to allow transcription of theheterologous gene. The DNA construct is recognized by the cellulartranscription machinery in a process that involves the activity of manytrans-acting transcription factors (TF) at cis-regulatory elements,including enhancers, silencers, insulators and promoters (hereinglobally referred to as “promoters”).

Gene promoter are involved in all of these levels of regulation, servingas the determinant in gene transcription by integrating the influencesof the DNA sequence, transcription factor binding and epigeneticfeatures. They determines the strength of e.g. transgene expressionwhich is encoded by a plasmid vector as well as in which cell type ortypes said transgene will be expressed.

The most common promoters used for driving heterologous gene expressionin mammalian cells are the human and mouse cytomegalovirus (CMV) majorimmediate early promoter. They confer a strong expression and haveproved robust in several cell types. Other viral promoters such as theSV40 immediate early promoter and the Rous Sarcoma Virus (RSV)long-terminal-repeat (LTR) promoter are also used frequently inexpression cassettes.

Instead of viral promoters, cellular promoters can also be used. Amongknown promoters are those from house-keeping genes that encodeabundantly transcribed cellular transcripts, such as beta-actin,elongation factor 1-alpha (EF-lalpha), or ubiquitin. Compared to viralpromoters, eukaryotic gene expression is more complex and requires aprecise coordination of many different factors.

One of the aspects concerning the use of endogenous regulatory elementsfor transgene expression is the generation of stable mRNA and thatexpression can take place in the native environment of the host cellwhere trans-acting transcription factors are provided accordingly. Sinceexpression of eukaryotic genes is controlled by a complex machinery ofcis- and trans-acting regulatory elements, most cellular promoterssuffer from a lack of extensive functional characterization. Parts ofthe eukaryotic promoter are usually located immediately upstream of itstranscribed sequence and serves as the point of transcriptionalinitiation. The core promoter immediately surrounds the transcriptionstart site (TSS) which is sufficient to be recognized by thetranscription machinery. The proximal promoter comprises the regionupstream of the core promoter and contains the TSS and other sequencefeatures required for transcriptional regulation. Transcription factorsact sequence-specific by binding to regulatory motifs in the promoterand enhancer sequence thereby activating chromatin and histone modifyingenzymes that alter nucleosome structure and its position which finallyallows initiation of transcription. The identification of a functionalpromoter is mainly dependent on the presence of associated upstream ordownstream enhancer elements.

Another crucial aspect concerning the use of endogenous regulatoryelements for transgene expression is that some promoters can act in acell specific manner and will lead to the expression of the transgene onin cells of a specific type or, depending on the promoter, in cells of aparticular subset.

Therefore, one goal of the present invention is to obtain new sequencessuitable for expressing recombinant genes in mammal cells of the retinawith high expression levels and in a cell type specific manner.

Such sequence address a need in the art for retinal cells specificpromoter to develop systems for the study of neurodegenerativedisorders, vision restoration, drug discovery, tumor therapies anddiagnosis of disorders.

SUMMARY OF THE INVENTION

The present inventors have now serendipitously found that an artificialpromoter which drives gene expression specifically in retinal amacrinecells. It is extremely useful to address and target gene expression inretinal AII (A2) amacrine cells in diseased retina.

The nucleic acid sequence of this sequence is:

(SEQ ID NO: 1) TCAAGCCTCCTACCGCCTTTGTTATGCAAACATATCAAACGCCCTCCTTTGTTATGCAAAAGGGCTGGAACGGGGCCTTTGTTATGCAAATCGCCCTCCCCGATCCCTTTGTTATGCAAATTTGACGAATTCCCACCTTTGTTATGCAAACAAATCTCCTACCCTCCTTTGTTATGCAAAGTGAGAGGGGCTGCACCTTTGTTATGCAAAATGCGGCCCCTGAGACCTTTGTTATGCAAAAACCATGTACGCTTGCCTTTGTTATGCAAACCGCCTGTTGCTTGGCCTTTGTTATGCAAAGCCACGCGATTGGCGCCTTTGTTATGCAAAGCTCGGTTATGTACACCTTTGTTATGCAAAGCTACTTTAAACTTGCCTTTGTTATGCAAATCACGACCTGACCGTCCTTTGTTATGCAAAAACGGTTGAAATAGTCCTTTGTTATGCAAAATGATATTGAATAGTCCTTTGTTATGCAAAAATTTAGATGCCGACCCTTTGTTATGCAAAGGAATGGGCGTGCTGCCTTTGTTATGCAAATTTTCGCTGCGACAGCCTTTGTTATGCAAACATGCTCGCCACTCACCTTTGTTATGCAAAGGTCTAACAATGACCCCTTTGTTATGCAAACTACGTGGAATAGATCCTTTGTTATGCAAACCCCGAGTTTTTGAACCTTTGTTATGCAAAATCAGTAACTTCATTCCTTTGTTATGCAAAATGTGACTTAACCTCCCTTTGTTATGCAA A.

The present invention hence provides an isolated nucleic acid moleculecomprising, or consisting of, the nucleic acid sequence of SEQ ID NO:1or a nucleic acid sequence of at least 400 bp having at least 70%identity to said nucleic acid sequence of SEQ ID NO:1, wherein saidisolated nucleic acid molecule specifically leads to the expression inretinal AII amacrine cells of a gene operatively linked to said nucleicacid sequence coding for said gene. In some embodiments, the nucleicacid sequence is at least 300 bp, at least 400 bp, at least 500 bp, atleast 600 bp, at least 700 bp, at least 800 bp, at least 900 bp, atleast 1000 bp, at least 1100 bp, at least 1200 bp, at least 1300 bp, atleast 1400 bp, at least 1500 bp, at least 1600 bp, at least 1700 bp, atleast 1800 bp, at least 1900 bp, or at least 2000 bp, and has at least80% identity to said nucleic acid sequence of SEQ ID NO:1. In someembodiments, the nucleic acid sequence is at least 300 bp, at least 400bp, at least 500 bp, at least 600 bp, at least 700 bp, at least 800 bp,at least 900 bp, at least 1000 bp, at least 1100 bp, at least 1200 bp,at least 1300 bp, at least 1400 bp, at least 1500 bp, at least 1600 bp,at least 1700 bp, at least 1800 bp, at least 1900 bp, or at least 2000bp, and has at least 85% identity to said nucleic acid sequence of SEQID NO:1. In some embodiments, the nucleic acid sequence is at least 300bp, at least 400 bp, at least 500 bp, at least 600 bp, at least 700 bp,at least 800 bp, at least 900 bp, at least 1000 bp, at least 1100 bp, atleast 1200 bp, at least 1300 bp, at least 1400 bp, at least 1500 bp, atleast 1600 bp, at least 1700 bp, at least 1800 bp, at least 1900 bp, orat least 2000 bp, and has at least 90% identity to said nucleic acidsequence of SEQ ID NO:1. In some embodiments, the nucleic acid sequenceis at least 300 bp, at least 400 bp, at least 500 bp, at least 600 bp,at least 700 bp, at least 800 bp, at least 900 bp, at least 1000 bp, atleast 1100 bp, at least 1200 bp, at least 1300 bp, at least 1400 bp, atleast 1500 bp, at least 1600 bp, at least 1700 bp, at least 1800 bp, atleast 1900 bp, or at least 2000 bp, and has at least 95% identity tosaid nucleic acid sequence of SEQ ID NO:1. In some embodiments, thenucleic acid sequence is at least 300 bp, at least 400 bp, at least 500bp, at least 600 bp, at least 700 bp, at least 800 bp, at least 900 bp,at least 1000 bp, at least 1100 bp, at least 1200 bp, at least 1300 bp,at least 1400 bp, at least 1500 bp, at least 1600 bp, at least 1700 bp,at least 1800 bp, at least 1900 bp, or at least 2000 bp, and has atleast 96% identity to said nucleic acid sequence of SEQ ID NO:1. In someembodiments, the nucleic acid sequence is at least 300 bp, at least 400bp, at least 500 bp, at least 600 bp, at least 700 bp, at least 800 bp,at least 900 bp, at least 1000 bp, at least 1100 bp, at least 1200 bp,at least 1300 bp, at least 1400 bp, at least 1500 bp, at least 1600 bp,at least 1700 bp, at least 1800 bp, at least 1900 bp, or at least 2000bp, and has at least 97% identity to said nucleic acid sequence of SEQID NO:1. In some embodiments, the nucleic acid sequence is at least 300bp, at least 400 bp, at least 500 bp, at least 600 bp, at least 700 bp,at least 800 bp, at least 900 bp, at least 1000 bp, at least 1100 bp, atleast 1200 bp, at least 1300 bp, at least 1400 bp, at least 1500 bp, atleast 1600 bp, at least 1700 bp, at least 1800 bp, at least 1900 bp, orat least 2000 bp, and has at least 98% identity to said nucleic acidsequence of SEQ ID NO:1. In some embodiments, the nucleic acid sequenceis at least 300 bp, at least 400 bp, at least 500 bp, at least 600 bp,at least 700 bp, at least 800 bp, at least 900 bp, at least 1000 bp, atleast 1100 bp, at least 1200 bp, at least 1300 bp, at least 1400 bp, atleast 1500 bp, at least 1600 bp, at least 1700 bp, at least 1800 bp, atleast 1900 bp, or at least 2000 bp, and has at least 99% identity tosaid nucleic acid sequence of SEQ ID NO:1. In some embodiments, thenucleic acid sequence is at least 300 bp, at least 400 bp, at least 500bp, at least 600 bp, at least 700 bp, at least 800 bp, at least 900 bp,at least 1000 bp, at least 1100 bp, at least 1200 bp, at least 1300 bp,at least 1400 bp, at least 1500 bp, at least 1600 bp, at least 1700 bp,at least 1800 bp, at least 1900 bp, or at least 2000 bp, and has 100%identity to said nucleic acid sequence of SEQ ID NO:1.

The isolated nucleic acid molecule of the invention can comprise aminimal promoter, for instance a SV40 minimal promoter, e.g. the SV40minimal promoter

(SEQ ID NO: 2) GCTCGAGATCTGCGATCTGCATCTCAATTAGTCAGCAACCATAGTCCCGCCCCTAACTCCGCCCATCCCGCCCCTAACTCCGCCCAGTTCCGCCCATTCTCCGCCCCATCGCTGACTAATTTTTTTTATTTATGCAGAGGCCGAGGCCGCCTCGGCCTCTGAGCTATTCCAGAAGTAGTGAGGAGGCTTTTTTGGAGGCC TAGGCTTTTGCAAA.

Also provided is an isolated nucleic acid molecule comprising a sequencethat hybridizes under stringent conditions to an isolated nucleic acidmolecule of the invention as described above.

The present invention also provides an expression cassette comprising anisolated nucleic acid of the invention as described above, wherein saidpromoter is operatively linked to at least a nucleic acid sequenceencoding for a gene to be expressed specifically in retinal amacrinecells.

The present invention further provides a vector comprising theexpression cassette of the invention. In some embodiments, said vectoris a viral vector.

The present invention also encompasses the use of a nucleic acid of theinvention, of an expression cassette of the invention or of a vector ofthe invention for the expression of a gene in retinal amacrine cells.

The present invention further provides a method of expressing gene inretinal AII amacrine cells comprising the steps of transfecting anisolated cell, a cell line or a cell population (e.g. a tissue) with anexpression cassette of the invention, wherein the gene to be expressedwill be expressed by the isolated cell, the cell line or the cellpopulation if said cell is, or said cells comprise, retinal amacrinecells. In some embodiments, the isolated cell, cell line or cellpopulation or tissue is human.

The present invention also provides an isolated cell comprising theexpression cassette of the invention. In some embodiments, theexpression cassette or vector is stably integrated into the genome ofsaid cell.

A typical gene which can be operatively linked to the promoter of theinvention is a gene encoding for a photoreceptor. For instance it can bea photosensitive molecule such as a channelrhodopsin or a halorhodopsin.

In addition, the present invention also provides a kit for expressinggene in retinal amarcine cells, which kit comprises an isolated nucleicacid molecule of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Targeted expression to AII (A2) amacrine cells in the rodentretina from promoter ID NO:3. Laser-scanning confocal microscope imagesof EGFP expression from the promoter comprising SEQ ID NO:1 3 weeksafter subretinal injection of AAV-synP12-ChR2-EGFP in adult C57BL/6mouse eyes. Induced expression in AII amacrine cells can be observed.Green=EGFP driven by the SEQ ID NO:3. Magenta=ChAT (CholineAcetyltransferase). White=Hoechst.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have now serendipitously found that an artificialpromoter which drives gene expression specifically in retinal amacrinecells. It is extremely useful to address and target gene expression inretinal AII amacrine cells in diseased retina.

The nucleic acid sequence of this sequence is:

(SEQ ID NO: 1) TCAAGCCTCCTACCGCCTTTGTTATGCAAACATATCAAACGCCCTCCTTTGTTATGCAAAAGGGCTGGAACGGGGCCTTTGTTATGCAAATCGCCCTCCCCGATCCCTTTGTTATGCAAATTTGACGAATTCCCACCTTTGTTATGCAAACAAATCTCCTACCCTCCTTTGTTATGCAAAGTGAGAGGGGCTGCACCTTTGTTATGCAAAATGCGGCCCCTGAGACCTTTGTTATGCAAAAACCATGTACGCTTGCCTTTGTTATGCAAACCGCCTGTTGCTTGGCCTTTGTTATGCAAAGCCACGCGATTGGCGCCTTTGTTATGCAAAGCTCGGTTATGTACACCTTTGTTATGCAAAGCTACTTTAAACTTGCCTTTGTTATGCAAATCACGACCTGACCGTCCTTTGTTATGCAAAAACGGTTGAAATAGTCCTTTGTTATGCAAAATGATATTGAATAGTCCTTTGTTATGCAAAAATTTAGATGCCGACCCTTTGTTATGCAAAGGAATGGGCGTGCTGCCTTTGTTATGCAAATTTTCGCTGCGACAGCCTTTGTTATGCAAACATGCTCGCCACTCACCTTTGTTATGCAAAGGTCTAACAATGACCCCTTTGTTATGCAAACTACGTGGAATAGATCCTTTGTTATGCAAACCCCGAGTTTTTGAACCTTTGTTATGCAAAATCAGTAACTTCATTCCTTTGTTATGCAAAATGTGACTTAACCTCCCTTTGTTATGCAA A.

The present invention hence provides an isolated nucleic acid moleculecomprising, or consisting of, the nucleic acid sequence of SEQ ID NO:1or a nucleic acid sequence of at least 400 bp having at least 70%identity to said nucleic acid sequence of SEQ ID NO:1, wherein saidisolated nucleic acid molecule specifically leads to the expression inretinal AII amacrine cells of a gene operatively linked to said nucleicacid sequence coding for said gene. In some embodiments, the nucleicacid sequence is at least 300 bp, at least 400 bp, at least 500 bp, atleast 600 bp, at least 700 bp, at least 800 bp, at least 900 bp, atleast 1000 bp, at least 1100 bp, at least 1200 bp, at least 1300 bp, atleast 1400 bp, at least 1500 bp, at least 1600 bp, at least 1700 bp, atleast 1800 bp, at least 1900 bp, or at least 2000 bp, and has at least80% identity to said nucleic acid sequence of SEQ ID NO:1. In someembodiments, the nucleic acid sequence is at least 300 bp, at least 400bp, at least 500 bp, at least 600 bp, at least 700 bp, at least 800 bp,at least 900 bp, at least 1000 bp, at least 1100 bp, at least 1200 bp,at least 1300 bp, at least 1400 bp, at least 1500 bp, at least 1600 bp,at least 1700 bp, at least 1800 bp, at least 1900 bp, or at least 2000bp, and has at least 85% identity to said nucleic acid sequence of SEQID NO:1. In some embodiments, the nucleic acid sequence is at least 300bp, at least 400 bp, at least 500 bp, at least 600 bp, at least 700 bp,at least 800 bp, at least 900 bp, at least 1000 bp, at least 1100 bp, atleast 1200 bp, at least 1300 bp, at least 1400 bp, at least 1500 bp, atleast 1600 bp, at least 1700 bp, at least 1800 bp, at least 1900 bp, orat least 2000 bp, and has at least 90% identity to said nucleic acidsequence of SEQ ID NO:1. In some embodiments, the nucleic acid sequenceis at least 300 bp, at least 400 bp, at least 500 bp, at least 600 bp,at least 700 bp, at least 800 bp, at least 900 bp, at least 1000 bp, atleast 1100 bp, at least 1200 bp, at least 1300 bp, at least 1400 bp, atleast 1500 bp, at least 1600 bp, at least 1700 bp, at least 1800 bp, atleast 1900 bp, or at least 2000 bp, and has at least 95% identity tosaid nucleic acid sequence of SEQ ID NO:1. In some embodiments, thenucleic acid sequence is at least 300 bp, at least 400 bp, at least 500bp, at least 600 bp, at least 700 bp, at least 800 bp, at least 900 bp,at least 1000 bp, at least 1100 bp, at least 1200 bp, at least 1300 bp,at least 1400 bp, at least 1500 bp, at least 1600 bp, at least 1700 bp,at least 1800 bp, at least 1900 bp, or at least 2000 bp, and has atleast 96% identity to said nucleic acid sequence of SEQ ID NO:1. In someembodiments, the nucleic acid sequence is at least 300 bp, at least 400bp, at least 500 bp, at least 600 bp, at least 700 bp, at least 800 bp,at least 900 bp, at least 1000 bp, at least 1100 bp, at least 1200 bp,at least 1300 bp, at least 1400 bp, at least 1500 bp, at least 1600 bp,at least 1700 bp, at least 1800 bp, at least 1900 bp, or at least 2000bp, and has at least 97% identity to said nucleic acid sequence of SEQID NO:1. In some embodiments, the nucleic acid sequence is at least 300bp, at least 400 bp, at least 500 bp, at least 600 bp, at least 700 bp,at least 800 bp, at least 900 bp, at least 1000 bp, at least 1100 bp, atleast 1200 bp, at least 1300 bp, at least 1400 bp, at least 1500 bp, atleast 1600 bp, at least 1700 bp, at least 1800 bp, at least 1900 bp, orat least 2000 bp, and has at least 98% identity to said nucleic acidsequence of SEQ ID NO:1. In some embodiments, the nucleic acid sequenceis at least 300 bp, at least 400 bp, at least 500 bp, at least 600 bp,at least 700 bp, at least 800 bp, at least 900 bp, at least 1000 bp, atleast 1100 bp, at least 1200 bp, at least 1300 bp, at least 1400 bp, atleast 1500 bp, at least 1600 bp, at least 1700 bp, at least 1800 bp, atleast 1900 bp, or at least 2000 bp, and has at least 99% identity tosaid nucleic acid sequence of SEQ ID NO:1. In some embodiments, thenucleic acid sequence is at least 300 bp, at least 400 bp, at least 500bp, at least 600 bp, at least 700 bp, at least 800 bp, at least 900 bp,at least 1000 bp, at least 1100 bp, at least 1200 bp, at least 1300 bp,at least 1400 bp, at least 1500 bp, at least 1600 bp, at least 1700 bp,at least 1800 bp, at least 1900 bp, or at least 2000 bp, and has 100%identity to said nucleic acid sequence of SEQ ID NO:1.

The isolated nucleic acid molecule of the invention can comprise aminimal promoter, for instance a SV40 minimal promoter, e.g. the SV40minimal promoter

(SEQ ID NO: 2) GCTCGAGATCTGCGATCTGCATCTCAATTAGTCAGCAACCATAGTCCCGCCCCTAACTCCGCCCATCCCGCCCCTAACTCCGCCCAGTTCCGCCCATTCTCCGCCCCATCGCTGACTAATTTTTTTTATTTATGCAGAGGCCGAGGCCGCCTCGGCCTCTGAGCTATTCCAGAAGTAGTGAGGAGGCTTTTTTGGAGGCC TAGGCTTTTGCAAA.

Also provided is an isolated nucleic acid molecule comprising a sequencethat hybridizes under stringent conditions to an isolated nucleic acidmolecule of the invention as described above.

The present invention also provides an expression cassette comprising anisolated nucleic acid of the invention as described above, wherein saidpromoter is operatively linked to at least a nucleic acid sequenceencoding for a gene to be expressed specifically in retinal amacrinecells.

The present invention further provides a vector comprising theexpression cassette of the invention. In some embodiments, said vectoris a viral vector.

The present invention also encompasses the use of a nucleic acid of theinvention, of an expression cassette of the invention or of a vector ofthe invention for the expression of a gene in retinal amacrine cells.

The present invention further provides a method of expressing gene inretinal AII amacrine cells comprising the steps of transfecting anisolated cell, a cell line or a cell population (e.g. a tissue) with anexpression cassette of the invention, wherein the gene to be expressedwill be expressed by the isolated cell, the cell line or the cellpopulation if said cell is, or said cells comprise, retinal amarinecells. In some embodiments, the isolated cell, cell line or cellpopulation or tissue is human.

The present invention also provides an isolated cell comprising theexpression cassette of the invention. In some embodiments, theexpression cassette or vector is stably integrated into the genome ofsaid cell.

A typical gene which can be operatively linked to the promoter of theinvention is a gene encoding for a photoreceptor. For instance it can bea photosensitive molecule such as a channelrhodopsin or a halorhodopsin.

In addition, the present invention also provides a kit for expressinggene in retinal amarcine cells, which kit comprises an isolated nucleicacid molecule of the invention.

As used herein, the term “promoter” refers to any cis-regulatoryelements, including enhancers, silencers, insulators and promoters.

Expression cassettes are typically introduced into a vector thatfacilitates entry of the expression cassette into a host cell andmaintenance of the expression cassette in the host cell. Such vectorsare commonly used and are well known to those of skill in the art.Numerous such vectors are commercially available, e.g., from Invitrogen,Stratagene, Clontech, etc., and are described in numerous guides, suchas Ausubel, Guthrie, Strathem, or Berger, all supra. Such vectorstypically include promoters, polyadenylation signals, etc. inconjunction with multiple cloning sites, as well as additional elementssuch as origins of replication, selectable marker genes (e.g., LEU2,URA3, TRP 1, HIS3, GFP), centromeric sequences, etc.

Viral vectors, for instance an AAV, a PRV or a lentivirus, are suitableto target and deliver genes to retinal AII amacrine cells using apromoter of the invention.

The output of retinal cells can be measured using an electrical method,such as a multi-electrode array or a patch-clamp, or using a visualmethod, such as the detection of fluorescence.

The methods using nucleic acid sequence of the invention can be used foridentifying therapeutic agents for the treatment of a neurologicaldisorder or of a disorder of the retina involving amacrine cells, saidmethod comprising the steps of contacting a test compound with retinalAII amacrine cells expressing one or more transgene under a promoter ofthe invention, and comparing at least one output of retinal AII amacrinecells obtained in the presence of said test compound with the sameoutput obtained in the absence of said test compound.

Moreover, the methods using promoters of the invention can also be usedfor in vitro testing of vision restoration, said method comprising thesteps of contacting retinal AII amacrine cells expressing one or moretransgene under the control of a promoter of the invention with anagent, and comparing at least one output obtained after the contact withsaid agent with the same output obtained before said contact with saidagent.

Channelrhodopsins are a subfamily of opsin proteins that function aslight-gated ion channels. They serve as sensory photoreceptors inunicellular green algae, controlling phototaxis, i.e. movement inresponse to light. Expressed in cells of other organisms, they enablethe use of light to control intracellular acidity, calcium influx,electrical excitability, and other cellular processes. At least three“natural” channelrhodopsins are currently known: Channelrhodopsin-1(ChR1), Channelrhodopsin-2 (ChR2), and Volvox Channelrhodopsin (VChR1).Moreover, some modified/improved versions of these proteins also exist.AII known Channelrhodopsins are unspecific cation channels, conductingH+, Na+, K+, and Ca2+ ions.

Halorhodopsin is a light-driven ion pump, specific for chloride ions,and found in phylogenetically ancient “bacteria” (archaea), known ashalobacteria. It is a seven-transmembrane protein of the retinylideneprotein family, homologous to the light-driven proton pumpbacteriorhodopsin, and similar in tertiary structure (but not primarysequence structure) to vertebrate rhodopsins, the pigments that senselight in the retina. Halorhodopsin also shares sequence similarity tochannelrhodopsin, a light-driven ion channel. Halorhodopsin contains theessential light-isomerizable vitamin A derivative all-trans-retinal.Halorhodopsin is one of the few membrane proteins whose crystalstructure is known. Halorhodopsin isoforms can be found in multiplespecies of halobacteria, including H. salinarum, and N. pharaonis. Muchongoing research is exploring these differences, and using them to parseapart the photocycle and pump properties. After bacteriorhodopsin,halorhodopsin may be the best type I (microbial) opsin studied. Peakabsorbance of the halorhodopsin retinal complex is about 570 nm.Recently, halorhodopsin has become a tool in optogenetics. Just as theblue-light activated ion channel channelrhodopsin-2 opens up the abilityto activate excitable cells (such as neurons, muscle cells, pancreaticcells, and immune cells) with brief pulses of blue light, halorhodopsinopens up the ability to silence excitable cells with brief pulses ofyellow light. Thus halorhodopsin and channelrhodopsin together enablemultiple-color optical activation, silencing, and desynchronization ofneural activity, creating a powerful neuroengineering toolbox.

In some embodiments, the promoter is part of a vector targeted a retina,said vector expressing at least one reporter gene which is detectable inliving retinal amacrine cells. Such reporter genes can be indicative ofa functioning neural circuit. Examples of such vectors are activitysensors or rainbow viruses (Nature Methods 6, 127-130 (2009)). Examplesof such viruses are retrograde, transsynaptic pseudorabies viruses(PRVs) with genetically encoded activity sensors that optically reportthe activity of connected neurons among spatially intermingled neuronsin the brain. Such activity sensor can be an isolated transsynapticvirus expressing an exogenous fluorescent activity sensor. Thetranssynaptic virus can be a rhabdovirus, e.g. rabies virus, or aherpesvirus, for instance an alphaherpesvirus, e.g. pseudorabies virus.

The fluorescent exogenous activity sensor can be a fluorescent proteinCa²⁺ sensor, e.g. yellow cameleon, camgaroo, G-CaMP/Pericam, or TN-L15,or a fluorescent protein voltage sensor, e.g. FlaSh, SPARC, or a VSP,preferably VSP1.

Suitable viral vectors for the invention are well-known in the art. Forinstance an AAV, a PRV or a lentivirus, are suitable to target anddeliver genes to retinal amacrine cells.

When working with isolated retina, optimal viral delivery forphotoreceptors can be achieved by mounting the ganglion cell sidedownwards, so that the photoreceptor side of the retina is exposed andcan thus be better transfected. Another technique is slicing, e.g. witha razor blade, the inner limiting membrane of the retina, such that thedelivering viruses can penetrate the inner membranes. A further way isto embed the retina in agar, slicing said retina and applying thedelivery viruses from the side of the slice.

The output of transfected cells can be measured using well-knownmethods, for instance using an electrical method, such as amulti-electrode array or a patch-clamp, or using a visual method, suchas the detection of fluorescence. In some cases, the inner limitingmembrane is removed by micro-surgery the inner limiting membrane. Inother cases, recording is achieved through slices performed to the innerlimiting membrane.

Any source of retinal cells can be used for the present invention. Insome embodiments of the invention, the retinal cells come from, or arein, a human retina. In other embodiments, the retina is from an animal,e.g. of bovine or of rodent origin. Human retina can be easily obtainedfrom cornea banks where said retinas are normally discarded after thedissection of the cornea. Adult human retina has a large surface (about1100 mm²) and can therefore be easily separated to a number ofexperimentally subregions. Moreover, retinas can also be used as anexquisite model for synaptic communication since the retina has synapsesthat are identical to the rest of the brain.

As used herein, the term “animal” is used herein to include all animals.In some embodiments of the invention, the non-human animal is avertebrate. Examples of animals are human, mice, rats, cows, pigs,horses, chickens, ducks, geese, cats, dogs, etc. The term “animal” alsoincludes an individual animal in all stages of development, includingembryonic and fetal stages. A “genetically-modified animal” is anyanimal containing one or more cells bearing genetic information alteredor received, directly or indirectly, by deliberate genetic manipulationat a sub-cellular level, such as by targeted recombination,microinjection or infection with recombinant virus. The term“genetically-modified animal” is not intended to encompass classicalcrossbreeding or in vitro fertilization, but rather is meant toencompass animals in which one or more cells are altered by, or receive,a recombinant DNA molecule. This recombinant DNA molecule may bespecifically targeted to a defined genetic locus, may be randomlyintegrated within a chromosome, or it may be extrachromosomallyreplicating DNA. The term “germ-line genetically-modified animal” refersto a genetically-modified animal in which the genetic alteration orgenetic information was introduced into germline cells, therebyconferring the ability to transfer the genetic information to itsoffspring. If such offspring in fact possess some or all of thatalteration or genetic information, they are genetically-modified animalsas well.

The alteration or genetic information may be foreign to the species ofanimal to which the recipient belongs, or foreign only to the particularindividual recipient, or may be genetic information already possessed bythe recipient. In the last case, the altered or introduced gene may beexpressed differently than the native gene, or not expressed at all.

The genes used for altering a target gene may be obtained by a widevariety of techniques that include, but are not limited to, isolationfrom genomic sources, preparation of cDNAs from isolated mRNA templates,direct synthesis, or a combination thereof.

A type of target cells for transgene introduction is the ES cells. EScells may be obtained from pre-implantation embryos cultured in vitroand fused with embryos (Evans et al. (1981), Nature 292:154-156; Bradleyet al. (1984), Nature 309:255-258; Gossler et al. (1986), Proc. Natl.Acad. Sci. USA 83:9065-9069; Robertson et al. (1986), Nature322:445-448; Wood et al. (1993), Proc. Natl. Acad. Sci. USA90:4582-4584). Transgenes can be efficiently introduced into the EScells by standard techniques such as DNA transfection usingelectroporation or by retrovirus-mediated transduction. The resultanttransformed ES cells can thereafter be combined with morulas byaggregation or injected into blastocysts from a non-human animal. Theintroduced ES cells thereafter colonize the embryo and contribute to thegermline of the resulting chimeric animal (Jaenisch (1988), Science240:1468-1474). The use of gene-targeted ES cells in the generation ofgene-targeted genetically-modified mice was described 1987 (Thomas etal. (1987), Cell 51:503-512) and is reviewed elsewhere (Frohman et al.(1989), Cell 56:145-147; Capecchi (1989), Trends in Genet. 5:70-76;Baribault et al. (1989), Mol. Biol. Med. 6:481-492; Wagner (1990), EMBOJ. 9:3025-3032; Bradley et al. (1992), Bio/Technology 10:534-539).

Techniques are available to inactivate or alter any genetic region toany mutation desired by using targeted homologous recombination toinsert specific changes into chromosomal alleles. As used herein, a“targeted gene” is a DNA sequence introduced into the germline of anon-human animal by way of human intervention, including but not limitedto, the methods described herein. The targeted genes of the inventioninclude DNA sequences which are designed to specifically alter cognateendogenous alleles.

In the present invention, “isolated” refers to material removed from itsoriginal environment (e.g., the natural environment if it is naturallyoccurring), and thus is altered “by the hand of man” from its naturalstate. For example, an isolated polynucleotide could be part of a vectoror a composition of matter, or could be contained within a cell, andstill be “isolated” because that vector, composition of matter, orparticular cell is not the original environment of the polynucleotide.The term “isolated” does not refer to genomic or cDNA libraries, wholecell total or mRNA preparations, genomic DNA preparations (includingthose separated by electrophoresis and transferred onto blots), shearedwhole cell genomic DNA preparations or other compositions where the artdemonstrates no distinguishing features of the polynucleotide/sequencesof the present invention. Further examples of isolated DNA moleculesinclude recombinant DNA molecules maintained in heterologous host cellsor purified (partially or substantially) DNA molecules in solution.Isolated RNA molecules include in vivo or in vitro RNA transcripts ofthe DNA molecules of the present invention. However, a nucleic acidcontained in a clone that is a member of a library (e.g., a genomic orcDNA library) that has not been isolated from other members of thelibrary (e.g., in the form of a homogeneous solution containing theclone and other members of the library) or a chromosome removed from acell or a cell lysate (e.g., a “chromosome spread”, as in a karyotype),or a preparation of randomly sheared genomic DNA or a preparation ofgenomic DNA cut with one or more restriction enzymes is not “isolated”for the purposes of this invention. As discussed further herein,isolated nucleic acid molecules according to the present invention maybe produced naturally, recombinantly, or synthetically.

“Polynucleotides” can be composed of single- and double-stranded DNA,DNA that is a mixture of single- and double-stranded regions, single-and double-stranded RNA, and RNA that is mixture of single- anddouble-stranded regions, hybrid molecules comprising DNA and RNA thatmay be single-stranded or, more typically, double-stranded or a mixtureof single- and double-stranded regions. In addition, polynucleotides canbe composed of triple-stranded regions comprising RNA or DNA or both RNAand DNA. Polynucleotides may also contain one or more modified bases orDNA or RNA backbones modified for stability or for other reasons.“Modified” bases include, for example, tritylated bases and unusualbases such as inosine. A variety of modifications can be made to DNA andRNA; thus, “polynucleotide” embraces chemically, enzymatically, ormetabolically modified forms.

The expression “polynucleotide encoding a polypeptide” encompasses apolynucleotide which includes only coding sequence for the polypeptideas well as a polynucleotide which includes additional coding and/ornon-coding sequence.

“Stringent hybridization conditions” refers to an overnight incubationat 42 degree C. in a solution comprising 50% formamide, 5×SSC (750 mMNaCl, 75 mM trisodium citrate), 50 mM sodium phosphate (pH 7.6),5×Denhardt's solution, 10% dextran sulfate, and 20 μg/ml denatured,sheared salmon sperm DNA, followed by washing the filters in 0.1×SSC atabout 50 degree C. Changes in the stringency of hybridization and signaldetection are primarily accomplished through the manipulation offormamide concentration (lower percentages of formamide result inlowered stringency); salt conditions, or temperature. For example,moderately high stringency conditions include an overnight incubation at37 degree C. in a solution comprising 6×SSPE (20×SSPE=3M NaCl; 0.2MNaH₂PO₄; 0.02M EDTA, pH 7.4), 0.5% SDS, 30% formamide, 100 pg/ml salmonsperm blocking DNA; followed by washes at 50 degree C. with 1×SSPE, 0.1%SDS. In addition, to achieve even lower stringency, washes performedfollowing stringent hybridization can be done at higher saltconcentrations (e.g. 5×SSC). Variations in the above conditions may beaccomplished through the inclusion and/or substitution of alternateblocking reagents used to suppress background in hybridizationexperiments. Typical blocking reagents include Denhardt's reagent,BLOTTO, heparin, denatured salmon sperm DNA, and commercially availableproprietary formulations. The inclusion of specific blocking reagentsmay require modification of the hybridization conditions describedabove, due to problems with compatibility.

The terms “fragment,” “derivative” and “analog” when referring topolypeptides means polypeptides which either retain substantially thesame biological function or activity as such polypeptides. An analogincludes a pro-protein which can be activated by cleavage of thepro-protein portion to produce an active mature polypeptide.

The term “gene” means the segment of DNA involved in producing apolypeptide chain; it includes regions preceding and following thecoding region “leader and trailer” as well as intervening sequences(introns) between individual coding segments (exons).

Polypeptides can be composed of amino acids joined to each other bypeptide bonds or modified peptide bonds, i.e., peptide isosteres, andmay contain amino acids other than the 20 gene-encoded amino acids. Thepolypeptides may be modified by either natural processes, such asposttranslational processing, or by chemical modification techniqueswhich are well known in the art. Such modifications are well describedin basic texts and in more detailed monographs, as well as in avoluminous research literature. Modifications can occur anywhere in thepolypeptide, including the peptide backbone, the amino acid side-chainsand the amino or carboxyl termini. It will be appreciated that the sametype of modification may be present in the same or varying degrees atseveral sites in a given polypeptide. Also, a given polypeptide maycontain many types of modifications. Polypeptides may be branched, forexample, as a result of ubiquitination, and they may be cyclic, with orwithout branching. Cyclic, branched, and branched cyclic polypeptidesmay result from posttranslation natural processes or may be made bysynthetic methods. Modifications include, but are not limited to,acetylation, acylation, biotinylation, ADP-ribosylation, amidation,covalent attachment of flavin, covalent attachment of a heme moiety,covalent attachment of a nucleotide or nucleotide derivative, covalentattachment of a lipid or lipid derivative, covalent attachment ofphosphotidylinositol, cross-linking, cyclization, denivatization byknown protecting/blocking groups, disulfide bond formation,demethylation, formation of covalent cross-links, formation of cysteine,formation of pyroglutamate, formylation, gamma-carboxylation,glycosylation, GPI anchor formation, hydroxylation, iodination, linkageto an antibody molecule or other cellular ligand, methylation,myristoylation, oxidation, pegylation, proteolytic processing (e.g.,cleavage), phosphorylation, prenylation, racemization, selenoylation,sulfation, transfer-RNA mediated addition of amino acids to proteinssuch as arginylation, and ubiquitination. (See, for instance,PROTEINS-STRUCTURE AND MOLECULAR PROPERTIES, 2nd Ed., T. E. Creighton,W. H. Freeman and Company, New York (1993); POSTTRANSLATIONAL COVALENTMODIFICATION OF PROTEINS, B. C. Johnson, Ed., Academic Press, New York,pgs. I-12 (1983); Seifter et al., Meth Enzymol 182:626-646 (1990);Rattan et al., Ann NY Acad Sci 663:48-62 (1992).)

A polypeptide fragment “having biological activity” refers topolypeptides exhibiting activity similar, but not necessarily identicalto, an activity of the original polypeptide, including mature forms, asmeasured in a particular biological assay, with or without dosedependency. In the case where dose dependency does exist, it need not beidentical to that of the polypeptide, but rather substantially similarto the dose-dependence in a given activity as compared to the originalpolypeptide (i.e., the candidate polypeptide will exhibit greateractivity or not more than about 25-fold less and, in some embodiments,not more than about tenfold less activity, or not more than aboutthree-fold less activity relative to the original polypeptide.)

Species homologs may be isolated and identified by making suitableprobes or primers from the sequences provided herein and screening asuitable nucleic acid source for the desired homologue.

“Variant” refers to a polynucleotide or polypeptide differing from theoriginal polynucleotide or polypeptide, but retaining essentialproperties thereof. Generally, variants are overall closely similar,and, in many regions, identical to the original polynucleotide orpolypeptide.

As a practical matter, whether any particular nucleic acid molecule orpolypeptide is at least 80%, 85%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, or100% identical to a nucleotide sequence of the present invention can bedetermined conventionally using known computer programs. A preferredmethod for determining the best overall match between a query sequence(a sequence of the present invention) and a subject sequence, alsoreferred to as a global sequence alignment, can be determined using theFASTDB computer program based on the algorithm of Brutlag et al. (Comp.App. Blosci. (1990) 6:237-245). In a sequence alignment the query andsubject sequences are both DNA sequences. An RNA sequence can becompared by converting U's to T's. The result of said global sequencealignment is in percent identity. Preferred parameters used in a FASTDBalignment of DNA sequences to calculate percent identity are:Matrix=Unitary, k-tuple=4, Mismatch Penalty—1, Joining Penalty—30,Randomization Group Length=0, Cutoff Score=I, Gap Penalty—5, Gap SizePenalty 0.05, Window Size=500 or the length of the subject nucleotidesequence, whichever is shorter. If the subject sequence is shorter thanthe query sequence because of 5′ or 3′ deletions, not because ofinternal deletions, a manual correction must be made to the results.This is because the FASTDB program does not account for 5′ and 3′truncations of the subject sequence when calculating percent identity.For subject sequences truncated at the 5′ or 3′ ends, relative to thequery sequence, the percent identity is corrected by calculating thenumber of bases of the query sequence that are 5′ and 3′ of the subjectsequence, which are not matched/aligned, as a percent of the total basesof the query sequence. Whether a nucleotide is matched/aligned isdetermined by results of the FASTDB sequence alignment. This percentageis then subtracted from the percent identity, calculated by the aboveFASTDB program using the specified parameters, to arrive at a finalpercent identity score. This corrected score is what is used for thepurposes of the present invention. Only bases outside the 5′ and 3′bases of the subject sequence, as displayed by the FASTDB alignment,which are not matched/aligned with the query sequence, are calculatedfor the purposes of manually adjusting the percent identity score. Forexample, a 90 base subject sequence is aligned to a 100 base querysequence to determine percent identity. The deletions occur at the 5′end of the subject sequence and therefore, the FASTDB alignment does notshow a matched/alignment of the first 10 bases at 5′ end. The 10impaired bases represent 10% of the sequence (number of bases at the 5′and 3′ ends not matched/total number of bases in the query sequence) so10% is subtracted from the percent identity score calculated by theFASTDB program. If the remaining 90 bases were perfectly matched thefinal percent identity would be 90%. In another example, a 90 basesubject sequence is compared with a 100 base query sequence. This timethe deletions are internal deletions so that there are no bases on the5′ or 3′ of the subject sequence which are not matched/aligned with thequery. In this case the percent identity calculated by FASTDB is notmanually corrected. Once again, only bases 5′ and 3′ of the subjectsequence which are not matched/aligned with the query sequence aremanually corrected for.

By a polypeptide having an amino acid sequence at least, for example,95% “identical” to a query amino acid sequence of the present invention,it is intended that the amino acid sequence of the subject polypeptideis identical to the query sequence except that the subject polypeptidesequence may include up to five amino acid alterations per each 100amino acids of the query amino acid sequence. In other words, to obtaina polypeptide having an amino acid sequence at least 95% identical to aquery amino acid sequence, up to 5% of the amino acid residues in thesubject sequence may be inserted, deleted, or substituted with anotheramino acid. These alterations of the reference sequence may occur at theamino or carboxy terminal positions of the reference amino acid sequenceor anywhere between those terminal positions, interspersed eitherindividually among residues in the reference sequence or in one or morecontiguous groups within the reference sequence.

As a practical matter, whether any particular polypeptide is at least80%, 85%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, or 100% identical to, forinstance, the amino acid sequences shown in a sequence or to the aminoacid sequence encoded by deposited DNA clone can be determinedconventionally using known computer programs. A preferred method fordetermining, the best overall match between a query sequence (a sequenceof the present invention) and a subject sequence, also referred to as aglobal sequence alignment, can be determined using the FASTDB computerprogram based on the algorithm of Brutlag et al. (Comp. App. Biosci.(1990) 6:237-245). In a sequence alignment the query and subjectsequences are either both nucleotide sequences or both amino acidsequences. The result of said global sequence alignment is in percentidentity. Preferred parameters used in a FASTDB amino acid alignmentare: Matrix=PAM 0, k-tuple=2, Mismatch Penalty—I, Joining Penalty=20,Randomization Group Length=0, Cutoff Score=1, Window Size=sequencelength, Gap Penalty—5, Gap Size Penalty—0.05, Window Size=500 or thelength of the subject amino acid sequence, whichever is shorter. If thesubject sequence is shorter than the query sequence due to N- orC-terminal deletions, not because of internal deletions, a manualcorrection must be made to the results. This is because the FASTDBprogram does not account for N- and C-terminal truncations of thesubject sequence when calculating global percent identity. For subjectsequences truncated at the N- and C-termini, relative to the querysequence, the percent identity is corrected by calculating the number ofresidues of the query sequence that are N- and C-terminal of the subjectsequence, which are not matched/aligned with a corresponding subjectresidue, as a percent of the total bases of the query sequence. Whethera residue is matched/aligned is determined by results of the FASTDBsequence alignment. This percentage is then subtracted from the percentidentity, calculated by the above FASTDB program using the specifiedparameters, to arrive at a final percent identity score. This finalpercent identity score is what is used for the purposes of the presentinvention. Only residues to the N- and C-termini of the subjectsequence, which are not matched/aligned with the query sequence, areconsidered for the purposes of manually adjusting the percent identityscore. That is, only query residue positions outside the farthest N- andC-terminal residues of the subject sequence. Only residue positionsoutside the N- and C-terminal ends of the subject sequence, as displayedin the FASTDB alignment, which are not matched/aligned with the querysequence are manually corrected for. No other manual corrections are tobe made for the purposes of the present invention.

Naturally occurring protein variants are called “allelic variants,” andrefer to one of several alternate forms of a gene occupying a givenlocus on a chromosome of an organism. (Genes 11, Lewin, B., ed., JohnWiley & Sons, New York (1985).) These allelic variants can vary ateither the polynucleotide and/or polypeptide level. Alternatively,non-naturally occurring variants may be produced by mutagenesistechniques or by direct synthesis.

“Label” refers to agents that are capable of providing a detectablesignal, either directly or through interaction with one or moreadditional members of a signal producing system. Labels that aredirectly detectable and may find use in the invention includefluorescent labels. Specific fluorophores include fluorescein,rhodamine, BODIPY, cyanine dyes and the like.

A “fluorescent label” refers to any label with the ability to emit lightof a certain wavelength when activated by light of another wavelength.

“Fluorescence” refers to any detectable characteristic of a fluorescentsignal, including intensity, spectrum, wavelength, intracellulardistribution, etc.

“Detecting” fluorescence refers to assessing the fluorescence of a cellusing qualitative or quantitative methods. In some of the embodiments ofthe present invention, fluorescence will be detected in a qualitativemanner. In other words, either the fluorescent marker is present,indicating that the recombinant fusion protein is expressed, or not. Forother instances, the fluorescence can be determined using quantitativemeans, e.g., measuring the fluorescence intensity, spectrum, orintracellular distribution, allowing the statistical comparison ofvalues obtained under different conditions. The level can also bedetermined using qualitative methods, such as the visual analysis andcomparison by a human of multiple samples, e.g., samples detected usinga fluorescent microscope or other optical detector (e.g., image analysissystem, etc.). An “alteration” or “modulation” in fluorescence refers toany detectable difference in the intensity, intracellular distribution,spectrum, wavelength, or other aspect of fluorescence under a particularcondition as compared to another condition. For example, an “alteration”or “modulation” is detected quantitatively, and the difference is astatistically significant difference. Any “alterations” or “modulations”in fluorescence can be detected using standard instrumentation, such asa fluorescent microscope, CCD, or any other fluorescent detector, andcan be detected using an automated system, such as the integratedsystems, or can reflect a subjective detection of an alteration by ahuman observer.

The “green fluorescent protein” (GFP) is a protein, composed of 238amino acids (26.9 kDa), originally isolated from the jellyfish Aequoreavictoria/Aequorea aequorea/Aequorea forskalea that fluoresces green whenexposed to blue light. The GFP from A. victoria has a major excitationpeak at a wavelength of 395 nm and a minor one at 475 nm. Its emissionpeak is at 509 nm which is in the lower green portion of the visiblespectrum. The GFP from the sea pansy (Renilla reniformis) has a singlemajor excitation peak at 498 nm. Due to the potential for widespreadusage and the evolving needs of researchers, many different mutants ofGFP have been engineered. The first major improvement was a single pointmutation (S65T) reported in 1995 in Nature by Roger Tsien. This mutationdramatically improved the spectral characteristics of GFP, resulting inincreased fluorescence, photostablility and a shift of the majorexcitation peak to 488 nm with the peak emission kept at 509 nm. Theaddition of the 37° C. folding efficiency (F64L) point mutant to thisscaffold yielded enhanced GFP (EGFP). EGFP has an extinction coefficient(denoted ϵ), also known as its optical cross section of 9.13×10-21m²/molecule, also quoted as 55,000 L/(mol·cm). Superfolder GFP, a seriesof mutations that allow GFP to rapidly fold and mature even when fusedto poorly folding peptides, was reported in 2006.

The “yellow fluorescent protein” (YFP) is a genetic mutant of greenfluorescent protein, derived from Aequorea victoria. Its excitation peakis 514 nm and its emission peak is 527 nm.

As used herein, the singular forms “a”, “an,” and the include pluralreference unless the context clearly dictates otherwise.

A “virus” is a sub-microscopic infectious agent that is unable to growor reproduce outside a host cell. Each viral particle, or virion,consists of genetic material, DNA or RNA, within a protective proteincoat called a capsid. The capsid shape varies from simple helical andicosahedral (polyhedral or near-spherical) forms, to more complexstructures with tails or an envelope. Viruses infect cellular life formsand are grouped into animal, plant and bacterial types, according to thetype of host infected.

The term “transsynaptic virus” as used herein refers to viruses able tomigrate from one neurone to another connecting neurone through asynapse. Examples of such transsynaptic virus are rhabodiviruses, e.g.rabies virus, and alphaherpesviruses, e.g. pseudorabies or herpessimplex virus. The term “transsynaptic virus” as used herein alsoencompasses viral sub-units having by themselves the capacity to migratefrom one neurone to another connecting neurone through a synapse andbiological vectors, such as modified viruses, incorporating such asub-unit and demonstrating a capability of migrating from one neurone toanother connecting neurone through a synapse.

Transsynaptic migration can be either anterograde or retrograde. Duringa retrograde migration, a virus will travel from a postsynaptic neuronto a presynaptic one. Accordingly, during anterograde migration, a viruswill travel from a presynaptic neuron to a postsynaptic one.

Homologs refer to proteins that share a common ancestor. Analogs do notshare a common ancestor, but have some functional (rather thanstructural) similarity that causes them to be included in a class (e.g.trypsin like serine proteinases and subtilisin's are clearly notrelated—their structures outside the active site are completelydifferent, but they have virtually geometrically identical active sitesand thus are considered an example of convergent evolution to analogs).

There are two subclasses of homologs—orthologs and paralogs. Orthologsare the same gene (e.g. cytochome ‘c’), in different species. Two genesin the same organism cannot be orthologs. Paralogs are the results ofgene duplication (e.g. hemoglobin beta and delta). If two genes/proteinsare homologous and in the same organism, they are paralogs.

As used herein, the term “disorder” refers to an ailment, disease,illness, clinical condition, or pathological condition.

As used herein, the term “pharmaceutically acceptable carrier” refers toa carrier medium that does not interfere with the effectiveness of thebiological activity of the active ingredient, is chemically inert, andis not toxic to the patient to whom it is administered.

As used herein, the term “pharmaceutically acceptable derivative” refersto any homolog, analog, or fragment of an agent, e.g. identified using amethod of screening of the invention, that is relatively non-toxic tothe subject.

The term “therapeutic agent” refers to any molecule, compound, ortreatment, that assists in the prevention or treatment of disorders, orcomplications of disorders.

Compositions comprising such an agent formulated in a compatiblepharmaceutical carrier may be prepared, packaged, and labeled fortreatment.

If the complex is water-soluble, then it may be formulated in anappropriate buffer, for example, phosphate buffered saline or otherphysiologically compatible solutions.

Alternatively, if the resulting complex has poor solubility in aqueoussolvents, then it may be formulated with a non-ionic surfactant such asTween, or polyethylene glycol. Thus, the compounds and theirphysiologically acceptable solvates may be formulated for administrationby inhalation or insufflation (either through the mouth or the nose) ororal, buccal, parenteral, rectal administration or, in the case oftumors, directly injected into a solid tumor.

For oral administration, the pharmaceutical preparation may be in liquidform, for example, solutions, syrups or suspensions, or may be presentedas a drug product for reconstitution with water or other suitablevehicle before use. Such liquid preparations may be prepared byconventional means with pharmaceutically acceptable additives such assuspending agents (e.g., sorbitol syrup, cellulose derivatives orhydrogenated edible fats); emulsifying agents (e.g., lecithin oracacia); non-aqueous vehicles (e.g., almond oil, oily esters, orfractionated vegetable oils); and preservatives (e.g., methyl orpropyl-p-hydroxybenzoates or sorbic acid). The pharmaceuticalcompositions may take the form of, for example, tablets or capsulesprepared by conventional means with pharmaceutically acceptableexcipients such as binding agents (e.g., pregelatinized maize starch,polyvinyl pyrrolidone or hydroxypropyl methylcellulose); fillers (e.g.,lactose, microcrystalline cellulose or calcium hydrogen phosphate);lubricants (e.g., magnesium stearate, talc or silica); disintegrants(e.g., potato starch or sodium starch glycolate); or wetting agents(e.g., sodium lauryl sulphate). The tablets may be coated by methodswell-known in the art.

Preparations for oral administration may be suitably formulated to givecontrolled release of the active compound.

For administration by inhalation, the compounds for use according to thepresent invention are conveniently delivered in the form of an aerosolspray presentation from pressurized packs or a nebulizer, with the useof a suitable propellant, e.g., dichlorodifluoromethane,trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide orother suitable gas. In the case of a pressurized aerosol the dosage unitmay be determined by providing a valve to deliver a metered amount.Capsules and cartridges of, e.g., gelatin for use in an inhaler orinsufflator may be formulated containing a powder mix of the compoundand a suitable powder base such as lactose or starch.

The compounds may be formulated for parenteral administration byinjection, e.g., by bolus injection or continuous infusion. Formulationsfor injection may be presented in unit dosage form, e.g., in ampoules orin multi-dose containers, with an added preservative.

The compositions may take such forms as suspensions, solutions oremulsions in oily or aqueous vehicles, and may contain formulatoryagents such as suspending, stabilizing and/or dispersing agents.Alternatively, the active ingredient may be in powder form forconstitution with a suitable vehicle, e.g., sterile pyrogen-free water,before use.

The compounds may also be formulated as a topical application, such as acream or lotion.

In addition to the formulations described previously, the compounds mayalso be formulated as a depot preparation. Such long acting formulationsmay be administered by implantation (for example, intraocular,subcutaneous or intramuscular) or by intraocular injection.

Thus, for example, the compounds may be formulated with suitablepolymeric or hydrophobic materials (for example, as an emulsion in anacceptable oil) or ion exchange resins, or as sparingly solublederivatives, for example, as a sparingly soluble salt. Liposomes andemulsions are well known examples of delivery vehicles or carriers forhydrophilic drugs.

The compositions may, if desired, be presented in a pack or dispenserdevice which may contain one or more unit dosage forms containing theactive ingredient. The pack may for example comprise metal or plasticfoil, such as a blister pack. The pack or dispenser device may beaccompanied by instructions for administration.

The invention also provides kits for carrying out the therapeuticregimens of the invention. Such kits comprise in one or more containerstherapeutically or prophylactically effective amounts of thecompositions in pharmaceutically acceptable form.

The composition in a vial of a kit may be in the form of apharmaceutically acceptable solution, e.g., in combination with sterilesaline, dextrose solution, or buffered solution, or otherpharmaceutically acceptable sterile fluid. Alternatively, the complexmay be lyophilized or desiccated; in this instance, the kit optionallyfurther comprises in a container a pharmaceutically acceptable solution(e.g., saline, dextrose solution, etc.), preferably sterile, toreconstitute the complex to form a solution for injection purposes.

In another embodiment, a kit further comprises a needle or syringe,preferably packaged in sterile form, for injecting the complex, and/or apackaged alcohol pad. Instructions are optionally included foradministration of compositions by a clinician or by the patient.

Amacrine cells represent the most diverse class of retinal neuron,comprising dozens of distinct cell types. Each type exhibits a uniquemorphology and generates specific visual computations through itssynapses with a subset of excitatory interneurons (bipolar cells), otheramacrine cells, and output neurons (ganglion cells). The AII (or A2)amacrine cells connect rod and cone photoreceptor pathways, forming anessential link in the circuit for rod-mediated (scotopic) vision. Assuch, the AII has become known as the rod-amacrine cell. The AIIfunction extends to cone-mediated (photopic) vision, and AII function inscotopic and photopic conditions utilizes the same underlying circuit:Alls are electrically coupled to each other and to the terminals of sometypes of ON cone bipolar cells. The direction of signal flow, however,varies with illumination. Under photopic conditions, the AII networkconstitutes a cross-over inhibition pathway that allows ON signals toinhibit OFF ganglion cells and contributes to motion sensitivity incertain ganglion cell types. The AII's combination of intrinsic andnetwork properties accounts for its unique role in visual processing.(Vis Neurosci. 2012 January; 29(1):51-60.)

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. In case of conflict, the presentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

EXAMPLES

Gene Construct

The promoter used in this example (964 bp; SEQ ID NO:3) consists of theone of SEQ ID NO:1 coupled to the minimal promoter SV40 promoter of SEQID NO:2. ChR2-eGFP coding sequence was inserted immediately after thispromoters and the optimized Kozak sequence (GCCACC), and followed by awoodchuck hepatitis virus posttranscriptional regulatory element (WPRE)and SV40 polyadenylation site. Retinal neurons were targeted using AAVsserotype 2/8 with a titer of 2.9E+10 GC/mL.

Viral Transfection and Tissue Preparation

For AAV administration, the eyes of anesthetized animals were puncturedin the sclera close to the lens by a sharp 30 gauge needle. 2 microL ofAAV particle suspension were injected subretinally by a Hamiltonsyringe. After 3 weeks, the isolated retinas were fixed for 30 min in 4%PFA in PBS, followed by a washing step in PBS at 4 degree C. Wholeretinas were treated with 10% normal donkey serum (NDS), 1% BSA, 0.5%Triton X-100 in PBS for 1 h at room temperature. Treatment withmonoclonal rat anti-GFP Ab (Molecular Probes Inc.; 1:500) and polyclonalgoat anti-ChAT (Millipore: 1:200) in 3% NDS, 1% BSA, 0.5% Triton X-100in PBS was carried out for 5 days at room temperature. Treatment withsecondary donkey anti-rat Alexa Fluor-488 Ab (Molecular Probes Inc.;1:200), anti-goat Alexa Fluor-633 and Hoechst, was done for 2 hr.Sections were washed, mounted with ProLong Gold antifade reagent(Molecular Probes Inc.) on glass slides, and photographed using a ZeissLSM 700 Axio Imager Z2 laser scanning confocal microscope (Carl ZeissInc.).

The invention claimed is:
 1. An isolated nucleic acid moleculecomprising the nucleic acid sequence of SEQ ID NO: 1, or a nucleic acidsequence having at least 95% identity to SEQ ID NO: 1, wherein theisolated nucleic acid molecule further comprises a minimal promoter thatis operably linked to the 3′ end of said nucleic acid sequence, andwherein said isolated nucleic acid molecule specifically leads to theexpression of a gene in retinal AII amacrine cells when said gene isoperatively linked to said isolated nucleic acid molecule.
 2. Theisolated nucleic acid molecule of claim 1, wherein the minimal promoteris the sequence of SEQ ID NO:
 2. 3. An expression cassette comprisingthe isolated nucleic acid molecule according to claim 1, wherein saidisolated nucleic acid molecule is operatively linked to at a gene to beexpressed specifically in retinal All amacrine cells.
 4. A vectorcomprising the expression cassette of claim
 3. 5. The vector of claim 4,wherein said vector is a viral vector.
 6. A method of expressing a genein retinal AII amacrine cells comprising the step of transfecting anisolated cell, a cell line or a cell population with the expressioncassette according to claim 3, wherein the gene is expressed by theisolated cell, the cell line or the cell population if said cell isretinal AII amacrine cell, or said cell line or said cell populationcomprises retinal AII amacrine cells.
 7. An isolated cell comprising theexpression cassette of claim
 3. 8. The cell of claim 7 wherein theexpression cassette or vector is stably integrated into the genome ofsaid cell.
 9. The isolated nucleic acid molecule of claim 1, wherein theproduct of the gene is a photoreceptor.
 10. A kit for expressing a genein retinal AII amacrine cells comprising the isolated nucleic acidmolecule according to claim
 1. 11. The isolated nucleic acid molecule ofclaim 1, wherein the nucleic acid sequence has at least 98% identity toSEQ ID NO:
 1. 12. The isolated nucleic acid molecule of claim 1, whereinthe nucleic acid sequence comprises the sequence of SEQ ID NO: 1.